package Demo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket = null;
    public UdpEchoServer(int port){
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            throw new RuntimeException(e);
        }
    }
    public void start() throws IOException {
        System.out.println("服务器启动");
        while(true){
            //1.读取客户端的请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request  = new String(requestPacket.getData(),0, requestPacket.getLength());
            //2.根据请求计算响应
            String response = process(request);
            //3.把响应写回客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("[%s:%d] req = %s,resp = %s",requestPacket.getAddress(),requestPacket.getPort(),request,response);
        }
    }
    private String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
